A 33-year-old mentally ill man killed his father here by hitting him with a pestle over a petty dispute, police said Tuesday.

The man also hit his mother when she intervened, before injuring himself with the same tool. Chandra Mohan alias Chinku killed his 58-year-old father Harnam Singh Dhingra in Krishna Nagar area of east Delhi Monday night.

When Kailash Rani, 55, his mother, tried to save her husband, Mohan started beating her as well, injuring her severely. Mohan then hit himself on the head with the pestle. "All of them were rushed to hospital, where Dhingra was declared brought dead while Rani's condition is stated to be critical," a police officer said.